Panel or panelette filters for removing particulate matter from fluids flowing through the filters are known in the art. For example, panel filters are commonly used in the automotive industry to remove particulate matter from air flowing through an air intake system into an internal combustion engine or from air flowing through a heating and/or air conditioning system into the interior cabin of a vehicle.
Panel filters can be regularly shaped, i.e., a square or rectangular shape, or irregularly shaped, i.e., a non-square or non-rectangular shape. Due to tighter constraints in the automotive industry, and in particular, the engine system of automobiles, it has become increasingly difficult to package and design regularly shaped filters that meet desirable performance characteristics and adequately fit within the confines of the engine system. Accordingly, filter manufacturers have increasingly moved to irregularly shaped filters, which provide more flexibility in filter and filter housing geometries to meet desirable performance characteristics and fit within the confines of the engine system.
Panel filters for automotive applications typically include at least one sheet of filtering media, such as paper, held in place by a frame or housing. The sheet of filter media typically has a plurality of pleats that extend from one end to an opposite end of the sheet. The pleats are sealed together at the ends of the filtering media sheet to prevent fluid from escaping from one side of the sheet to the other without traveling through the filter. The pleats can be sealed together using any of several methods. For example, in some conventional filters, the filtering media sheet is potted into or sealingly inserted into the filter frame using plastisol or urethane. In other conventional filters, a bonding adhesive, such as hot melt, is applied to the ends of the pleated sheet prior to securing the sheet to the frame or housing. Generally, hot melt sealing typically results in a lower pressure drop across the filter and thus is preferred over other sealing methods.
Mass producing filter media using continuous pleating process techniques involves feeding a continuous roll of paper through an apparatus in a paper feed direction and forming the continuous sheet into a plurality of individual filter sheets. Although hot melt sealing can be used to manufacture regularly shaped panel filters using conventional continuous pleating process techniques, it is not practical for the manufacturing of irregularly shaped filters using the same conventional techniques for various reasons. For example, in conventional continuous pleating process techniques, the pleats are gathered together in a gathering station after the hot melt is applied to the ends of the sheets, which are parallel to paper feed direction. Many rollers are required to force the pleats to gather. The rollers must avoid contact with the hot melt to prevent damage to the seal. With regularly shaped filters, the rollers can grab the sheet at all locations between the ends of the paper because the hot melt is positioned at the ends of the sheet. If, however, the sheet is irregularly shaped, one or more of the ends of the sheets are angled or curved toward each other (see, e.g., FIGS. 4 and 5). Therefore, the rollers, which avoided the hot melt on regularly shaped filters, would roll directly over the hot melt on irregularly shaped filters, thus potentially damaging the seal. Accordingly, a need exists for the ability to manufacture irregularly shaped and hot melt sealed panel filters using continuous pleating process techniques.